Unresolved inflammation involving cells of the blood vessel wall plays a crucial role in the pathogenesis of atherosclerosis. Therefore, discovery of novel therapeutic strategies against atherosclerosis requires an in- depth understanding of the endogenous mechanisms adopted by vascular cells to resolve inflammation. Using cell-based and murine models we showed that genetic deficiency of L13a in macrophages leads to uncontrolled inflammation and resultant disease, perhaps by abrogation of L13a-dependent translational silencing of a group of mRNAs encoding inflammatory proteins e.g., chemokines and chemokine receptors. Macrophage-specific L13a-knockout (KO) mice fail to resolve inflammation upon induction of experimental endotoxemia and breeding these mice on an apoE-/- background and subsequent challenge with a high-fat diet showed significantly increased atherosclerosis. We also showed that in monocytes/macrophages, the release of L13a from the 60S ribosomal subunit and its assembly into the IFN-?-activated inhibitor of translation (GAIT) complex which binds to the GAIT element located in the 3? untranslated region (UTR) of target mRNAs, is essential for translational silencing. However the GAIT element from one target mRNA does not efficiently compete with the GAIT elements of other target mRNAs for the binding to GAIT complexes. This suggests either different affinities of the same GAIT complex for those elements or the presence of distinct L13a- containing GAIT complexes. Together, these results lead us to hypothesize that the presence of appropriate L13a-containing GAIT complexes and their binding to cognate GAIT elements of the target mRNAs leads to resolution of inflammation and prevention of atherosclerosis by preventing alterations of the cellular landscape of vascular plaques and circulating leukocytes. We will test our hypothesis by pursuing the following three specific aims: (1) Testing the impact of L13a deficiencies on the cellular landscapes of vascular plaques as well as on circulating and tissue leukocytes. In this aim using L13a-KO animals we will undertake a comprehensive analysis of L13a-depleted macrophages and test their ability to mobilize, metabolize cholesterol, present antigen, engagement in phagocytic activity, polarization and Nlrp3 inflammasome activation. (2) Testing the heterogeneity of the cis-acting GAIT elements and RNA-binding GAIT complexes. In this aim we will perform RNA-binding analysis for competition studies and RNA-affinity purification to identify new accessory proteins in the GAIT complex (3) Studies of the mechanisms of ribosomal incorporation of L13a in primary cells. In this aim we will complement the L13a-/- fibroblasts from embryo and L13a-/- macrophages from macrophage-specific L13a-KO mice with wild type and ribosome incorporation-defective mutants to study the subcellular localization of this protein and its interactions with other assembly factors.